The construction, decoration and eruption of your students' volcanoes require a significant number of materials. Mix two tablespoons of flour with two tablespoons of tap water to produce a thick and consistent papier-maché for each student building a volcano. Give students paint brushes so they can apply papier-maché to newspaper. Students also require a square of thick cardboard approximately 20 x 20 inches, five double pages of old newspaper, a reel of masking tape, and an empty two-liter drink bottle to construct their volcanoes. Supply youngsters with brown, green and white paint; a paintbrush; and a pot of water to decorate their volcanoes. They will also need four tablespoons of baking soda, a cup of vinegar, and half a medicine dropper of red food coloring when they are ready to make their models erupt.
Students must first place the two-liter bottle in the middle of their cardboard square. Instruct students to run masking tape from the very rim of the bottle diagonally downwards to within an inch of the edge of the cardboard square. Make sure students apply masking tape all the way around the bottle so there are no gaps. Youngsters should then tear their newspaper pages into inch-wide strips along their length, daub them in papier-maché, and lay them atop the masking tape so they run from the rim of the bottle down to the base of the cardboard. Once the volcanoes are covered, students should leave them in a warm, dry environment for at least 24 hours so they can dry and harden.
Your young scientists should now use their brown, green and white paint to decorate their volcanoes. Help them achieve this by pinning up pictures of different volcanoes around the classroom for inspiration. Get students to paint colors one-by-one, or wash their paintbrushes thoroughly in a pot of water before switching between colors. Once students are happy with their painting effort, they should leave their volcanoes in a warm, dry place to dry off.
On the day of the science fair, get students to move their volcanoes so they are displayed prominently in their stalls. Students should also lay down a tarpaulin on their stalls or even move the volcano outdoors as the replica eruption is sure to make a mess. To start their eruption, students should place a funnel in the neck of the bottle at the center of the volcano and add four tablespoons of baking soda and half a medicine dropper of red food coloring. With a crowd of science fair judges and classmates assembled, students should then add a cup of vinegar before quickly removing the funnel and retreating a few steps to enjoy the eruption. More advanced students should also explain the chemical reaction to their audience as the acid (vinegar) meets the base (the sodium bicarbonate in the baking soda) which react to produce carbon dioxide.